1. Field of the Invention
The invention generally relates to wood products and, more particularly, relates to methods of manufacturing consolidated cellulosic panels.
2. Description of Related Technology
Consolidated cellulosic panels, such as fiber board, paper board, particle board, and the like, are typically comprised of wood furnish such as saw dust, shavings, chips, or specially ground fibers, compressed with a binding agent or resin under heat and pressure. Such boards can be used in a variety of applications including, but not limited to, exterior house siding, interior and exterior door facing panels or door skins, cabinet doors, paneling, moulding, etc.
It is often desirable to manufacture such panels to a uniform basis weight and caliper. If the panels are flat this can be accomplished by compressing a mat between first and second flat faced dies. However, if one of the faces needs to be deeply contoured, such die compressions have proven to be problematic. For example, if a first die has a contour corresponding to the desired shape of the panel, and the second die has a flat face, the mat compressed therebetween will have a non-uniform caliper, with the thinner areas of the mat being compressed to a higher density than thicker areas. This is especially true with fiberous materials that do not flow under pressure.
Current methods of producing such panels therefore typically require that a mat having first and second opposed flat surfaces be compressed according to conventional methods, and that one or more of the surfaces then be machined to have the desired contour. For example, a router may be used to shape the surfaces. U.S. Pat. No. 4,175,106, assigned to the present assignee, discloses such a process. Such tools, however, cannot easily produce sharp inside corners, are relatively slow, and require complex, expensive equipment.
Another method requires contoured, complementary, dies on both the top and bottom to produce a substantially uniform thickness through the contoured and non-contoured areas. If one of the top or bottom needs to be flat, or alternatively shaped, the panel must undergo an added machining step adding time, expense and waste to the operation. Shallow contouring of one face is typically done in an embossing operation, or with an embossing die, but the depth of embossing is greatly limited.
In accordance with one aspect of the invention, a method for producing a consolidated cellulosic article is provided. The method comprises the steps of providing a mat of cellulosic material and binder resin, providing a first contoured front platen having a first pattern, providing a first contoured rear platen having a pattern generally corresponding to the pattern of the front platen, consolidating the mat between the front platen and the rear platen under heat and pressure to form a molded softboard having a contoured front surface and a correspondingly contoured rear surface, the softboard having a substantially uniform density and a substantially uniform caliper, removing portions of the molded softboard to form a softboard having a front surface and a rear surface with desired contours, providing a second contoured front platen having a contour substantially corresponding to the contour of the front surface, providing a second contoured platen having a contour substantially corresponding to the contour of the rear surface, and consolidating the softboard between the second contoured front platen and the second contoured rear platen under heat and pressure.
In accordance with another aspect of the invention, a method of producing a consolidated cellulosic article is provided comprising the steps of compressing a mat of cellulosic material and a binder resin between first and second contoured platens to produce a softboard having first and second opposed contoured sides, removing cellulosic material from the softboard along one of the first or second sides in a planar fashion, and subsequently compressing the mat between third and fourth platens, the third platen being contoured in a manner similar to the first side of the softboard, the fourth platen being contoured in a manner similar to the second side of the softboard.
In accordance with another aspect of the invention, a system for producing a consolidated cellulosic article is provided comprising a primary press, a removal tool, and a secondary press. The primary press includes first and second platens and a drive with the first and second platens having opposed, complementarily contoured, die surfaces. The drive is adapted to compress the first and second platens toward one another. The removal tool includes a blade for removal of cellulosic material in a planar fashion. The secondary press has first and second platens and a drive. The first and second platens have opposed die surfaces. The drive is adapted to compress the first and second platens toward one another.
These and other aspects and features of the invention will become more apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings.